SE have been fighting this issue since release.

The issue is that they are trying to keep their game accessible to a wide audience to maximise business profits, while meeting the demands of players screaming "give us harder content".
It's only natural that a little (read: a lot) from column A, find themselves sneaking over into column B.

I am all for people trying as much of the game's content as they can.. However they should also recognise when they are the ones causing problems in the party and try and iron out those problems.